Fritsch Roland, Collin Shaun P, Michiels Nico K
Animal Evolutionary Ecology, Department of Biology, Institute of Evolution and Ecology, University of Tübingen, Tübingen, Germany.
The Oceans Institute, The University of Western Australia, Crawley, WA, Australia.
Front Neuroanat. 2017 Dec 12;11:122. doi: 10.3389/fnana.2017.00122. eCollection 2017.
The environment and lifestyle of a species are known to exert selective pressure on the visual system, often demonstrating a tight link between visual morphology and ecology. Many studies have predicted the visual requirements of a species by examining the anatomical features of the eye. However, among the vast number of studies on visual specializations in aquatic animals, only a few have focused on small benthic fishes that occupy a heterogeneous and spatially complex visual environment. This study investigates the general retinal anatomy including the topography of both the photoreceptor and ganglion cell populations and estimates the spatial resolving power (SRP) of the eye of the Mediterranean triplefin . Retinal wholemounts were prepared to systematically and quantitatively analyze photoreceptor and retinal ganglion cell (RGC) densities using design-based stereology. To further examine the retinal structure, we also used magnetic resonance imaging (MRI) and histological examination of retinal cross sections. Observations of the triplefin's eyes revealed them to be highly mobile, allowing them to view the surroundings without body movements. A rostral aphakic gap and the elliptical shape of the eye extend its visual field rostrally and allow for a rostro-caudal accommodatory axis, enabling this species to focus on prey at close range. Single and twin cones dominate the retina and are consistently arranged in one of two regular patterns, which may enhance motion detection and color vision. The retina features a prominent, dorso-temporal, convexiclivate fovea with an average density of 104,400 double and 30,800 single cones per mm, and 81,000 RGCs per mm. Based on photoreceptor spacing, SRP was calculated to be between 6.7 and 9.0 cycles per degree. Location and resolving power of the fovea would benefit the detection and identification of small prey in the lower frontal region of the visual field.
已知一个物种的环境和生活方式会对视觉系统施加选择压力，这常常表明视觉形态与生态之间存在紧密联系。许多研究通过检查眼睛的解剖特征来预测一个物种的视觉需求。然而，在大量关于水生动物视觉特化的研究中，只有少数研究关注那些占据异质且空间复杂视觉环境的小型底栖鱼类。本研究调查了地中海三鳍鱼眼睛的一般视网膜解剖结构，包括光感受器和神经节细胞群体的地形图，并估计了其眼睛的空间分辨能力（SRP）。制备视网膜整装片，使用基于设计的体视学系统地、定量地分析光感受器和视网膜神经节细胞（RGC）的密度。为了进一步检查视网膜结构，我们还使用了磁共振成像（MRI）和视网膜横截面的组织学检查。对三鳍鱼眼睛的观察发现，它们的眼睛具有高度的可动性，使它们能够在不移动身体的情况下观察周围环境。眼睛的吻侧无晶状体间隙和椭圆形形状使视野向吻侧扩展，并允许有一个吻尾调节轴，使该物种能够聚焦近距离的猎物。单锥和双锥在视网膜中占主导地位，并始终以两种规则模式之一排列，这可能会增强运动检测和色觉。视网膜有一个突出的、背颞侧、凸面中央凹，平均每毫米有104,400个双锥和30,800个单锥，以及每毫米81,000个RGC。根据光感受器间距，计算出SRP在每度6.7至9.0周之间。中央凹的位置和分辨能力将有利于检测和识别视野下额叶区域的小型猎物。
